python实现读取文件的断点续传

python读取文件有两个重要的方法f.tell()和f.seek()

通过这两个方法就可以实现文件的断点续传，tell可以实时返回读取文件的偏移量，seek可以直接跳转到这个偏移量

只要在异常中断之前将文件的偏移量记录下来，之后继续执行的时候就可以从这个偏移量开始读起，

备注：从中间开始移动指针在读文件的时候必须以二进制的方式读

 

import json
from time import sleep

import requests

url = 'http://api.map.baidu.com/geocoder/v2/?address={addr_name}&output=json&ak=6HDoKGOxh5Yo5RRRNqAk8R9S6mcY9REY'


def get_jw(addr_name):
    result = requests.get(url.format(addr_name=addr_name))
    result_str = str(result.content, encoding="utf-8")
    rj = json.loads(result_str)
    lng = rj['result']['location']['lng']
    lat = rj['result']['location']['lat']
    return ','.join([addr_name, str(lng), str(lat)])


if __name__ == '__main__':
    file_name = '/opt/test/wangbin/community_copy.txt'
    target_file='/opt/test/wangbin/target2.txt'
    with open(file_name, 'rb') as f,open(target_file,'a') as f2:
        line = f.readline().strip()
        while line:
            line=str(line,encoding='utf8')
            id,community_name=line.split(',')
            addr_name = '杭州市' + community_name
            try:
                target=get_jw(addr_name)
                print(target)
                f2.write(id+','+target+'\n')
            except Exception as e:
                print(e)
                offset=len(line.encode('utf8'))+1
                f.seek(-offset,1)
            line=f.readline().strip()